In such projection television apparatus it is essential to provide some form of protection for the projection tubes should the line deflection current through one of the line deflection coils cease or substantially reduce or such field deflection current through one of the field deflection coils cease or substantially reduce. In a previous arrangement where the line deflection coils were connected in parallel a single sensing means was provided to determine the magnitude of the total deflection current supplied by the line output stage such that a change in the line deflection current due to one of the line deflection coils becoming open circuit would be used to control the protection circuit. With such an arrangement the magnitude of the total deflection currents had to be measured and due allowance had to be made for any normal changes in each individual deflection current.